Light induced structural changes in CH3NH3PbI3 Perovskite Solar Cells

Perovskite solar cells have recently become one of the most promising alternative to the current solar cell technologies by achieving efficiencies superior to 20%. Owing to their distortable structure these devices have proven to show unusually slow relaxation processes upon illumination. We have identified this phenomenon in the frequency domain by impedance spectroscopy (IS) and in the time domain by transient photovoltage decay (TPD) and open circuit voltage decay (OCVD). However the origin of this process is still unclear although three main hypotheses have been proposed in the literature: i) high internal electric field, ii) ferroelectric domains and iii) ion/defect diffusion. In this conference paper we first present our works on light induced structural changes in perovskite and then discuss the main hypotheses previously mentioned with the insight of first principle calculations.